The overall goal of the proposed research is to gain a detailed understanding of the mechanism of action of the alkali cation transport system and the associated (Na ion plus K ion) - ATPase, both with respect to the role of the protein and the role of the lipids. General methods will be developed for the study of lipid-protein interactions in membranes. This will be approached by the following methods: (1) detailed thermodynamic and kinetic studies of the ATPase, (2) synthesis of spin-labeled substrate and inhibitor analogs, (3) synthesis of spin-labeled lipid and phospholipid analogs, (4) use of nmr and epr techniques to investigate lipid-protein interactions, (5) development of the use of nitroxide biradicals for the determination of atomic scale distances in membrane proteins and as sensitive probes of membrane structural changes related to function, (6) development of amidinonitroxides as sensitive probes of pH and dielectric constant, and (7) development of the use of high dielectric organic solvents as tools for the purification of membrane proteins.